With peritoneal dialysis, a catheter is used for the supply and removal of dialysis liquid to/from the peritoneal cavity.
A commonly-used catheter is the so-called Tenckhoff-catheter which can be of the straight type or the spiral-shaped type. This catheter consists of a silicon tube, on to which are fastened two dacron pads, to which peritoneal fibres may grow attached, thereby fixing the catheter in position after surgical implantation.
The proximal end of the catheter is connected by means of a connector to a dialysis liquid supply arrangement. The distal end of the catheter is provided with a plurality of holes in its sidewall and generally ends in an opening.
One problem with this catheter is that the holes in the catheter can be blocked during the outward-feed phase, due to the effect of the suction pressure. During the inward-feed phase, too high flows can lead to the catheter moving into the peritoneal cavity. The force which occurs when the fluid flows out causes the tip of the catheter to lash about and to be displaced when the flow is initiated. This catheter migration is one of the reasons for a catheter having to be changed. This movement can also affect the peritoneal membrane's susceptibility to infection.
The liquid also flows out of the catheter through the side holes and, if the flow speed in the sideways direction is too high, discomfort to the patient may result. The flow speed in the forward direction may also cause the patient discomfort.
Catheters for different purposes are described in patent literature. For example, the patent document EP-A1-185 865 relates to an implantable intraperitoneal catheter provided with several spacers in the form of discs which protect the holes in the side of the catheter from becoming blocked by ingrowth. The spacers probably also have a protective effect on the peritoneal membrane which is kept away from the holes where the out-feed flow speed is at its largest. The distal end of the catheter is normally closed but may also be open.
The patent document EP-B1-381 062 describes a catheter for even distribution of therapeutic fluids and comprises a catheter with a plurality of holes along the catheter's sidewall. The diameter of the holes increases towards the distal end of the catheter which is closed. The very small holes are manufactured by laser technology and are rectangular or oblong.
The patent document WO 89/02290 describes a catheter for placement in the ventricular system in the brain. The catheter comprises many small holes which are drilled at an angle with respect to the normal, vis-a-vis the catheter wall.
The patent document U.S. Pat. No. 5,057,073 describes a double-lumen catheter for implanting into a patient's vein, for use with hemodialysis treatments. The catheter implanted with the help of a Seldinger thread and the catheter's distal end tip opening is formed with a restriction in order to fit around the Seldinger thread. The wall of the catheter is provided with a plurality of holes for the passage of blood into, and out of, the catheter.
The patent document EP-B1-191 234 discloses a process for providing a medical tube with grooves or slits.
With a straight catheter for peritoneal dialysis having an open distal end, a large part of the total flow, as much as two-thirds, will pass out through the tip opening. High outflow speeds thereby result, which could damage the fibres in the peritoneum. Additionally, the force which acts on the tip of the catheter due to the outflow of fluid in an axial direction becomes excessively high. It is this force which causes the catheter to lash about and be displaced when the flow is initiated. It is desirable to reduce this force, particularly at higher flows.
The problem is greater for shorter catheters with fewer side holes and with straight catheters. With higher mass flows, the proportion which flows out through the tip becomes larger when viewed as a percentage. If the flow is doubled, the outflow speed through the open tip is more than twice as high and the resulting force more than quadruples.